Relay

ABSTRACT

A relay which is operable at very low power levels and which is highly versatile in its applications is shown to be characterized by high gain and high reliability and by simplicity of structure. The relay comprises a first terminal mounted on a base of electrically insulating material and a second electrically conductive member having a terminal portion secured to the base, having a contact arm movable between an open circuit position spaced from the first terminal and a closed circuit position engaging the first terminal, and having integral spring portions connecting the contact arm and terminal portion of the second member for normally biasing the contact arm to one of the noted circuit positions. The relay also includes an actuator wire secured between the base and the contact arm of the second member. The actuator wire is formed of a nickel-titanium alloy and is adapted to be deformed from an original length to a second length as the contact arm is moved to the one circuit position in response to the noted spring bias while the wire material displays a relatively low modulus of elasticity below a transition temperature. The actuator wire is also adapted to abruptly return to its original length and to display a relatively higher modulus of elasticity to move the contact arm to the other circuit position against the spring bias when the wire material is heated above its transition temperature. Means are provided for electrically self-heating the actuator wire to its transition temperature when relay operation is desired.

United States Patent 1191 Clarke 1 RELAY [75] Inventor: David E. Clarke,Attleboro, Mass.

[73] Assignee: Texas Instruments Incorporated,

Dallas, Tex.

22 Filed: Apr. 16, 1973 211 Appl. No.: 351,750

[52] U.S. Cl 337/140, 337/l3l, 337/395 [51] Int. Cl. H0lh 61/06 [58]Field of Search 337/140, 145, 41, 123,

337/124,125,126,127,128,129,l30,131, 132,133,l35,l36,138,139, 140,382,393,

[56] References Cited UNlTED STATESPATENTS 2,761,931 9/1956 Schmidinger337/135 2,838,645 6/1958 Welch 337/41 X 3,037,102 5/1962 Schmidinger...337/140 X 3,111,566 11/1963 Jaidinger 337/140 X 3,180,954 4/1965Collette et al. 337/137 3,405,380 10/1968 Riebs 337/41 X 3,461,4248/1969 Kayuha, Jr 337/140 X 3,516,082 6/1970 Cooper 337/140 UX 3,634,803l/l972 Wilson et al.... 337/140 X 3,652,969 3/1972 Willson 337/1403,676,815 7/1972 Du Rocher 337/140 3.739314 6/1973 Rouvre et a1. 337/140Primary Examiner-Arthur T. Grimley Attorney-Agent, 0r Firm-HaroldLevine; John A. Haug; James P. McAndrews 1 1 Mar. 18, 1975 [57] ABSTRACTA relay which is operable at very low power levels and which is highlyversatile in its applications is shown to be characterized by high gainand high reliability and by simplicity of structure. The relay comprisesa first terminal mounted on a base of electrically insulating materialand a second electrically conductive member having a terminal portionsecured to the base, having a contact arm movable between an opencircuit position spaced from the first terminal and a closed circuitposition engaging the first terminal, and having integral springportions connecting the contact arm and terminal portion of the secondmember for normally biasing the contact arm to one of the noted circuitpositions. The relay also includes an actuator wire secured between thebase and the contact arm of the second member. The actuator wire isformed of a nickel-titanium alloy and is adapted to be deformed from anoriginal length toa second length as the contact arm is moved to the onecircuit position in response to the noted spring bias while the wirematerial displays a relatively low modulus of elasticity below atransition temperature. The actuator wire is also adapted to abruptlyreturn to its original length and to display a relatively higher modulusof elasticity to move the contact arm to the other circuit positionagainst the spring bias when the wire material is heated above itstransition temperature. Means are provided for electrically self-heatingthe actuator wire to its transition temperature when relay operation isdesired.

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' Z0 I I 1 /4 M 52 1 RELAY With the development of increasingly morecompact and inexpensive control systems which are operable at very lowpower levels, it becomes possible to incorporate an increasing number ofcontrol functions within the control system while still retainingreasonable system costs. However, for these control system advantages tobe achieved in practice, the systems must be utilized with improvedrelays which are capable of operating at low power levels, which providethe high gain necessary for performing various individual controlfunctions, and which are of compact, reliable and inexpensiveconstruction.

It is an object of this invention to provide novel and improvedelectrical relays; to provide suchrelays which are operable at very lowpower levels; to provide such relays which display very high gain; andto provide such relays which are of compact, reliable, versatile andinexpensive construction.

Other objects and advantages of the novel and improved relays of thisinvention appear in the following detailed description of preferredembodiments of this invention, the detailed description referring to thedrawings in which:

FIG. 1 is a plan view of a preferred embodiment of the relay of thisinvention;

FIG. 2 is a front elevation view of the relay shown in FIG. 1;

FIG. 3 is an end elevation view of the relay shown in FIG. 1;

FIG. 4 is a section view along line 44 of FIG. 1;

FIG. 5 is a partial section view to enlarged scale along line 5-5 ofFIG. 1;

FIG. 6 is a perspective view of a component of the relay of FIG. 1;

FIG. 7 is a section view similar to FIG. 4 illustrating an alternateembodiment of the relay of this invention; and

FIG. 8 is a section view similar to FIG. 4 illustrating anotheralternate embodiment of the relay of this invention.

Referring to FIGS. 1-5 of the drawing, 10 indicates v a preferredembodiment of the relay of this invention which is shown to include abase member 12 of a strong, rigid, electrically insulating material suchas a phenolic resin. Preferably, as shown, the base has a flat, bottomportion 12.1 and a generally U-shaped wall portion formed by upstandingwalls 12.2, 12.3 and 12.4, the end wall 12.3 preferably having anaperture 12.5 therein receiving an electrically conductive outputterminal member 14. The terminal 14 is secured in the aperture 12.5 by apress fit or in other conventional manner and extends in cantileverrelation over the base bottom to support a first, stationary, outputelectrical contact 16.

In accordance with this invention, the relay 10 also includes a secondelectrically conductive member 18, best shown in FIG. 6, whichintegrally incorporates an output terminal portion 18.1 including twoleg portions 18.2 and 18.3, a contact arm portion 18.4, and a pair ofspring portions 18.5 and 18.6 which connect the contact arm 18.4 to therespective legs 18.2 and 18.3 of the terminal portion of the secondconductive member. In a particularly inexpensive embodiment of thisinvention, the second conductive member 18 also includes an integraltang portion 18.7 upstanding from the contact arm, the tang preferablyhaving reentrant surfaces thereon as indicated at 18.8 in FIG. 6.

In accordance with this invention, the second conductive member 18 isformed of beryllium copper or phosphor bronze or other electricallyconductive spring material and carries a second output contact 20 at thedistal end of the contact arm 18.4. The conductive member 18 is securedto the base 12 by cementing or in other conventional manner fordisposing the contact 20 over the contact 16 as is best shown in FIG. 4.In this arrangement, the tang 18.7 and the contact arm 18.4 form abell-crank element which is pivotably movable around an axis (indicatedby the broken line 22 in FIG. 1) formed by the spring portions 18.5 and18.6 of the conductive member. The contact arm 18.4 is normally disposedout of the general plane of the second conductive member 18 by deformingof the spring portions 18.5 and 18.6 as is best illustrated in FIG. 5.Accordingly, the contact arm 18.4 is normally biased to the open circuitposition illustrated in FIG. 4 so that the contact 20 carried by thecontact arm is normally separated or disengaged from the mating outputcontact 16'. However, the contact arm 18.4 is adapted to be moved to aclosed circuit position wherein the contact 20 engages the contact 16with selected contact pressure. In this regard, where the tang 18.7 ofthe second conductive member is relatively shorter than the contact arm18.4, rotational movement of the bell-crank element formed by the tangand arm around the axis 22 requires relatively limited linear movementof the tang to provide fairly substantial movement of the movable outputcontact 20. As will be understood, the terminal 14 and the terminalportion 18.1 of the second conductive member are adapted to be connectedto a device diagrammatically indicated in FIG. 1 by the terminals 24 and26 so that the device is energized when the output circuit formed by theterminal 14 and the conductive member 18 is closed by engagement of thecontacts 16 and 20.

In -a preferred embodiment of this invention, a second base component28, also preferably formed of phenolic resin or other electricallyinsulating material and also of generally U-shaped configuration, isthen secured to the other side of the conductive member 18. Two relaycontrol terminals 30, preferably comprising screws threadedly engagedwith the base component 28, are then preferably recessed into grooves28.1 in the second base component. An actuator wire 32 is then securedin electrically conductive relation between the control terminals 30 toextend around the tang 18.7 of the second conductive member 18.Preferably a length of electrically insulating tubing 34 is fitted overthe actuator wire 32 as shown for electrically insulating the actuatorwire from the second conductive member. In this way, the controlterminals 30 are adapted to be connected to a control system, indicatedin FIG. 1 by the terminals 36 and 38, for selectively directingelectrical current through the metal actuator wire 32 when desired.

In accordance with this invention, the actuator wire 32 is preferablyformed of a selected nickel-titanium alloy commonly called Nitinolhaving a composition, by weight, of from about 54 to 56 percent nickeland the balance titanium. As this metal alloy is well known, the alloyis not further described herein and it will be understood that the alloyis adapted to display a relatively low modulus of elasticity below acharacteristic transitiontemperature and to display a relatively muchhigher modulus of elasticity when the wire material is heated above thenoted transition temperature, this change in properties being reversibleas the wire material is cooled below the transition temperature. Whenproperly conditioned in well known manner, the noted alloy is alsoadapted to display remarkable shape memory properties. That is, when thematerial of the wire 32 is deformed while below its transitiontemperature as by stret'ching'the wire to increase the-wire length up toabout 8- p'ercent, the wireis adapted to shorten abruptly and to returnto its original length when the wire is heated above its transitiontemperature. After cooling, the wire is againadapted to be deformed toagain prepare the wire for displaying its shape memory. Typically, forexample, the wire 32 is formed of a nickel-titanium alloy comprisingabout 55 percent nickel, by weight, and the balance titanium, this alloyhaving a transition temperature at about 60C. and having alternately,the wire 32 is formed of other known metal alloys-capable of displayingsimilar shape memory and modulus of elasticity properties.

lnthe relay 10 of this invention, the spring proper ties of theconductive member l8are selected so that, with the material of theactuator wire 32 below its transition temperature, the spring portions185 and 18.6 of'the second conductive member apply sufficient force tothe wire [32 to deform the wire to increase the wire length, preferablyby at least about 4 percent, and to normally bias the contact arm 18.4to the open circuit position shown in FIG. 4 to hold the contact disen-'gaged from the'contact 16. However, when electrical current isselectively directed through the wire 32 between the relay controlterminals for electrically self-heating the material of the wire aboveits transition temperature, the wireis sharply or abruptly shortenedinjlength returning to its original configuration and is sharplyincreased in modulus of elasticity for moving the contact arm 18.4 toits closed circuit position against the bias ofthe spring portions 18.5and 18.6 to engage the contact 20 with its mating contact 16 for closingthe output circuit of the relay. When the wire 321is thereafter.permitted to cool below its transition temperature,'whereby the modulusof elasticity of the wire material returns to its low initial level, thespring portions 18.5 and 18.6 again deform the wire to increase i'tslength and again return the contact arm 18.4 to its open circuitposition. As will be understood, the spring portion 18.5 and 18.6 of thesecond conductive member are initially deformed to a selectedex'tent asillustrated in FIG. 5 for adjusting the tension the spring portionsapply to the wire 32 and for adjusting the contact pressure between thecontacts 20 and 16 when Preferably the wire has a cross-sectionalarealess than about 1.5 X 10 square inches and typically the wire has adiameter of about 0.002inc'hes and a length of about 2 inches. As aresult, the wire is adapted to be heated from room temperature to itstransition temperature with very low input of electrical energy at lowcurrent levels but is adapted to provide significant movement of thecontact arm 18.4 and to apply substantial contact pressure between thecontacts 20 and 16 so that the relay can switch substantial currents.Thus, the relay is operable at very low power levels but provides veryhigh gain. Typically, for example, where the wire has a diameter of0.002 inches and a length of 2 inches, the relay l0 is operable at apower level below 2 watts and preferably below 0.5 watts but displays avery high gain, preferably greater than about 500 to l and preferably onthe order of 10,000 to. l, and can switch 50 amperes at I20 volts acrossthe contacts 20 and 16. The relay 10 is also of compact, reliable andvery inexpensive construction. In addition, the relay is very versatilein its applications. Note that, as illustrated by the broken lines 40 inFIG. 2, a plurality of the relays 10 are adapted to be stacked togetherin a very compact package. I

Further, various alternate embodiments of the relay 10 are also includedwithin the scope of this invention as is illustrated in FIGS. 7 and 8.That is, referring to FIG. 7 wherein components of the relay 42 showntherein which are comparable to components of the relay l0 ae identifiedwith corresponding reference numerals, the relay 42 is shown toinclude'a base 12 supporting a first output terminal 14 to carry acontact 16 as in the relay '10. In addition, howeventhe second baseelement 28 is also provided with an aperture 28.2

and a second output terminal 44 is mounted in this aperture to supportanother output contact 46. The second conductive member '18 is thenprovided withan additional contact 48 as shown. Preferably, the tang18.7 of the conductive member- 18' previously 'described, is-alsoreplaced by a bell-crank arm member 50 of electrically insulatingmaterial which is secured to the contact arm 18.4 by a screw 52 or thelike and which carries aboss 54, also preferably comprising a screwthreadedly engaged with the bell-crank'arm 50, around which the actuatorwire 32 extends. In the relay 42, the contacts 46 and 48 are normallyengaged for closing a first output circuit of the relay while thecontacts 20 and 16 are disengaged leaving a second output circuit of therelay open. However, when the acturator wire 32 is heated above itstransition temperature by directing electrical current through the wire,the contact arm 18.4 moves as in the relay 10 to engage the contacts 16and 20 for closing the second output circuit and to open the firstoutput circuit of the relay.

Referring now to FIG. 8, wherein corresponding reference numerals areagain used, the relay 56'illustrated in this drawing figure as shown toinclude a base member 12 supporting a first output terminal 14 carryinga contact 16. A first conductive member I8 is then secured to the base12 as in relay 10. Another base element 58 having an aperture 58.1receiving a second output terminal 60 carrying a contact 62 is thenmounted on the conductive member 18, the contact 62 being orientedupwardly as shown in FIG. 8. An additional conductive member 18 is thenmounted on the second base element 58 for disposing its contact 20 to Abe engaged with the output contact 62. A base element 28 is then securedon top of this additional conductive member 18 as shown in H0. 8.Neither of the conductive members 18 embodied in the relay 56 isprovided with a tang 18.7 but bell-crank arm elements 64 and 66 aresecured to the conductive members 18 by a screw 52 and by a pin 68 sothat the two contact arms 18.4 are arranged to move together. Theactuator wire 32 is then extended around a screw boss 54 as in the relay42. In this arrangement, two relay output circuits are normally open.However, when the actuator wire 32 is heated above its transitiontemperature, the wire shortens in length to move both contact arms 18.4to engage one of the contacts 20 with the contact 16 and to engage theother circuit 20 with the contact 62 for closing two output circuits ofthe relay.

Of course other modifications and equivalents of the described relays10, 42 and 56 are also within the scope of this invention. For example,the terminal 14, the

, conductive member 18 and the control terminals 30 of the relay couldall be mounted on a single base element having the general configurationof the end wall 12.3 of the base described with reference to relay 10for significantly reducing the size and weight of the relay. Other suchmodifications would be recognized by persons skilled in the art. Itshould be understood that this invention includes all modifications andequivalents of the disclosed embodiments falling within the scope of theappended claims.

I claim:

1. A relay comprising electrically insulating base means. a firstconductive member mounted on said base means. a second conductive memberformed of a single sheet of electrically conductive sheet materialhaving a pair of spaced first portions secured to said base means,having a contact arm portion extending in cantilever relation from theremainder of said second member between said first portions of saidsecond member and movable at its distal end between an open circuitposition spaced from said first conductive member and a closed circuitposition engaging said first conductive member, and having spring meansintegrally formed in said sheet material-respectively connecting saidfirst member portions with an opposite end of said contact arm portionof said second conductive member and normally biasing said contact armportion to one of said circuit positions, and an actuator wire elementsecured between said opposite end of said contact arm portion and saidbase means, said actuator element being formed of a metal alloy adaptedto be deformed from an original configuration to a second configurationas said contact arm portion is moved to said one circuit position bysaid spring bias while said metal alloy displays a relatively lowmodulus of elasticity below a transition temperature and to abruptlyreturn to said original configuration and to display a relatively higherof elasticity to move said contact arm portion to the other of saidcircuit positions against said spring bias when said metal alloy isheated above said transition temperature.

2. A relay as set forth in claim 1 wherein said actuator element isformed of a nickel-titanium alloy.

3. A relay as set forth in claim 2 wherein said nickeltitanium alloy hasa composition, by weight, of from about 54 to 56 percent nickel and thebalance titanium.

4. A relay as set forth in claim 3 wherein said actuator elementcomprises a wire of said nickel-titanium alloy having a cross-sectionalarea of less than about 1.5 X 10 square inches.

5. A relay comprising a base means of electrically insulating materialhaving a bottom and having a pair of upstanding side walls and an endwall forming a base wall portion of generally U-shaped configuration, afirst electrically conductive terminal member cantilever mounted on saidend wall and mounting a first electrical contact at the distal endthereof over said bottom of said base means, a second member formed of asingle sheet of electrically conductive spring material having aterminal portion including two leg portions thereof secured to said sidewalls of said base means, having a contact arm portion extending incantilever relation from the remainder of said second member andmounting a second electrical contact means thereon at the distal end ofsaid-contact arm portion for movement between an open circuit positionspaced from said first contact and a closed circuit position engagingsaid first contact, and having spring portions integrally formed fromsaid sheet material extending between respective leg portions and anopposite end of said contact arm portion of said second conductivemember over said bottom of said base means and normally biasing saidcontact arm portion to said open circuit position, a bell-crank armsecured to said opposite end of said contact arm portion and rotatablewith said contact arm portion around an axis extending through saidspring portions, control terminals secured to said base means, and ametal actuator wire connected between said control terminals and securedin electrically conductive relation to said bellcrank arm, said wirebeing formed of a nickel-titanium alloy adapted to be deformed from anoriginal length to a greater length as said contact arm portion is movedto said open circuit position in response to said spring bias while saidalloy .displays a relatively low modulus of elasticity below atransition temperature and to abruptly return to its original length andto display a relatively higher modulus of elasticity to rotate saidcontact arm and bellcrank-arm on said axis to move said contact armportion to said closed circuit position against said spring bias whensaid alloy is heated above said transition temperature by directingelectrical current through said wire between said control terminals.

6. A relay as set forth in claim 5 having an additional electricallyconductive terminal member cantilever mounted on said base means andmounting an additional electrical contact at the distal end thereof tonormally engage said second contact means and to be disengaged from saidsecond means when said actuator wire is heated to said transitiontemperature.

7. A relay as set forth in claim 5 having a plurality of said conductiveterminal members mounting respective electrical contacts and mounted onsaid base means, having a plurality of said members of electricallyconductive spring material mounted on said base means and havingrespective contacts mounted on the contact arm portions thereof, andhaving means for connecting said contact arm portions of said springmembers together for common movement to engage respective spring membercontacts with respective contacts mounted on said terminal members.

1. A relay comprising electrically insulating base means, a firstconductive member mounted on said base means, a second conductive memberformed of a single sheet of electrically conductive sheet materialhaving a pair of spaced first portions secured to said base means,having a contact arm portion extending in cantilever relation from theremainder of said second member between said first portions of saidsecond member and movable at its distal end between an open circuitposition spaced from said first conductive member and a closed circuitposition engaging said first conductive member, and having spring meansintegrally formed in said sheet material respectively connecting saidfirst member portions with an opposite end of said contact arm portionof said second conductive member and normally biasing said contact armportion to one of said circuit positions, and an actuator wire elementsecured between said opposite end of said contact arm portion and saidbase means, said actuator element being formed of a metal alloy adaptedto be deformed from an original configuration to a second configurationas said contact arm portion is moved to said one circuit position bysaid spring bias while said metal alloy displays a relatively lowmodulus of elasticity below a transition temperature and to abruptlyreturn to said original configuration and to display a relatively higherof elasticity to move said contact arm portion to the other of saidcircuit positions against said spring bias when said metal alloy isheated above said transition temperature.
 2. A relay as set forth inclaim 1 wherein said actuator element is formed of a nickel-titaniumalloy.
 3. A relay as set forth in claim 2 wherein said nickel-titaniumalloy has a composition, by weight, of from about 54 to 56 percentnickel and the balance titanium.
 4. A relay as set forth in claim 3wherein said actuator element comprises a wire of said nickel-titaniumalloy having a cross-sectional area of less than about 1.5 X 10 5 squareinches.
 5. A relay comprising a base means of electrically insulatingmatErial having a bottom and having a pair of upstanding side walls andan end wall forming a base wall portion of generally U-shapedconfiguration, a first electrically conductive terminal membercantilever mounted on said end wall and mounting a first electricalcontact at the distal end thereof over said bottom of said base means, asecond member formed of a single sheet of electrically conductive springmaterial having a terminal portion including two leg portions thereofsecured to said side walls of said base means, having a contact armportion extending in cantilever relation from the remainder of saidsecond member and mounting a second electrical contact means thereon atthe distal end of said contact arm portion for movement between an opencircuit position spaced from said first contact and a closed circuitposition engaging said first contact, and having spring portionsintegrally formed from said sheet material extending between respectiveleg portions and an opposite end of said contact arm portion of saidsecond conductive member over said bottom of said base means andnormally biasing said contact arm portion to said open circuit position,a bell-crank arm secured to said opposite end of said contact armportion and rotatable with said contact arm portion around an axisextending through said spring portions, control terminals secured tosaid base means, and a metal actuator wire connected between saidcontrol terminals and secured in electrically conductive relation tosaid bell-crank arm, said wire being formed of a nickel-titanium alloyadapted to be deformed from an original length to a greater length assaid contact arm portion is moved to said open circuit position inresponse to said spring bias while said alloy displays a relatively lowmodulus of elasticity below a transition temperature and to abruptlyreturn to its original length and to display a relatively higher modulusof elasticity to rotate said contact arm and bell-crank arm on said axisto move said contact arm portion to said closed circuit position againstsaid spring bias when said alloy is heated above said transitiontemperature by directing electrical current through said wire betweensaid control terminals.
 6. A relay as set forth in claim 5 having anadditional electrically conductive terminal member cantilever mounted onsaid base means and mounting an additional electrical contact at thedistal end thereof to normally engage said second contact means and tobe disengaged from said second means when said actuator wire is heatedto said transition temperature.
 7. A relay as set forth in claim 5having a plurality of said conductive terminal members mountingrespective electrical contacts and mounted on said base means, having aplurality of said members of electrically conductive spring materialmounted on said base means and having respective contacts mounted on thecontact arm portions thereof, and having means for connecting saidcontact arm portions of said spring members together for common movementto engage respective spring member contacts with respective contactsmounted on said terminal members.